Process for upgrading thiophosphates



United States Patent 3,309,432 PROCESS FOR UPGRADING THIOPHOSPHATESJackson Pollard English, Princeton, N.J., assignor to American CyanamidCompany, Stamford, Conn., a corporation of Maine No Drawing. Filed Oct.23, 1965, Ser. No. 504,182

I 10 Claims. (Cl. 260-989) The present invention relates to a novelprocess for upgrading pesticidal thiophosphates. More particularly, itrelates to a process for upgrading malodorous pesticidal thiophosphatesby substantially removing the offensive odor therefrom. Still moreparticularly, the invention is concerned with a method for treatingthiophosphate pesticides with selective aldehydes defined withparticularity hereinbelow to obtain storage-stable, odor improvedthiophosphates.

In the past, various methods for the elimination or masking of offensiveOdOIS in thiophosphate pesticide have been disclosed in the literature.Unfortunately, none has been wholly successful. kor instance, it isknown the useful ozonization process for successfully deodorizingmalathion, that is, O,( )-dimethyl-S-(1,2-di-'carbethoxyethyl)-phosphorodithioate as succinctly described in US.Letters Patent No. 2,980,723, cannot be universally employed for thetreatment of thiophosphate pesticides. Ozonization of illustrativethiophosphates, such as 0,0-dialkyl-S-(alkylthio)alkylphosphorodithioates causes rapid degradation of such compounds.Moreover, it has been observed that certain masking agents, such as pineand lavender scents are only partially effective for stabilizing odor ofparticular thiophosphates. Further, they do not achieve the desiredlevel of odor control necessary to classify a treated product as pre--mium grade. Still others, such as spice scent, can produce an intenseodor unlike that of the treated material but equally offensive. If aprocess whereby a storagestable, deodorized thiophosphate pesticidecould be provided eliminating the difficulties of the prior such aprocess would satisfy a long-felt need.

It is, therefore, a principal object of the invention to eliminaterather than mask the offensive odor generally attributable tothiophosphate pesticides. It is a further object of the invention toprovide a relatively simple, effective and economical method forreducing offensive odors in malodorous thiophosphate pesticides havingassociated therewith small amounts of at least an alkyl mercaptan. It isa still further object of the invention to provide a process for thereduction or prevention of the development of alkyl mercaptans inthiophasphate pesticides. Other objects and advantages will becomeapparent to one skilled in the art from a consideration of the ensuingdescription.

To this end, there is provided a relatively straightforward, simple andeffective method for attaining a marked improvement in malodorousthiophosphate pesticides. Unexpectedly, the improvement is attained byadmixing small amounts of selected aldehydes with the malodorousthiophosphate pesticides. Admixture can take place over a wide range oftemperatures, usually between 0 C. and 100 C. Surprisingly, theso-treated malodorous thiophosphate is markedly improved and remainsstorage-stable with respect to odor over a prolonged period of time.

According to the present invention, any commercially availablethiophosphate pesticide can be subjected to the action of an aldehyde inwhich said aldehyde is at least slightly soluble in the thiophosphateand in which the formed aldehyde-mercaptan derivative is of relativelyhigh boiling point. In general, the addition of from about 0.5% to about5% by weight of said selective aldepractice,

3,309,432 Patented Mar. 14, 1967 hyde to a malodorous thiophosphate issuflicient to reduce offensive odors of such thiophosphate to acommercially acceptable level. However, when utilizing an amount inexcess of 5% of the aldehyde, it is found that the use of such amount isundesirable, since the cost is increased and little, if any, additionaladvantage either by way of increasing the level, or extending theperiod, of odor control is attained.

Advantageously, a large variety of thiophosphate pesticides can betreated in accordance with theprocess of the invention. Illustrative ofsuch thiophosphates are:

and equivalents thereof.

Exemplary aldehydes which are characterized as being at least slightlysoluble is each of the above thiophosphate pesticides illustrated aboveand which form mercaptanaldehyde derivatives of relatively high boilingpoint are: ethyl glyoxylate, acetaldehyde, paraldehyde, benzaldehyde,methylprotocatechuic aldehyde, ethylprotocatechuic aldehyde,p-tolualdehyde, salicylaldehyde, furaldehyde and a-methylacrylicaldehyde. The preferred aldehydes are ethyl glyoxylate andmethylprotocatechuic aldehyde, since the latter readily react withoutdifiiculty with mercapt-ans normally present in thiophosphatepesticides. Significantly, the mercaptan content of the thiophosphate isappreciably reduced, thereby enhansing its odor characteristics.

It is an advantage that the process of the present invention eliminatesthe need for considerable specialized equipment and utilizes relativelyinexpensive equipment operable over a wide temperature range. Ingeneral, the aldehyde can be added prior to, during or subsequent to thepreparation of the thiophosphate being treated. Deodorization isattained upon the addition of the selective aldehyde within a relativelyshort period of time, usually from about fifteen minutes to about threehours.

The invention will be illustrated in conjunction with the followingexamples which are to be taken as illustrative only and not by way oflimitation.

Example 1 The reduction of methyl mercaptan in malathion by treatmentwith small amounts of a selective aldehyde is demonstrated by utilizingtwelve individual compositions of malathion containing methyl mercaptan.To each individual composition is added from about 0.1% to about 2% byweight of diverse selective aldehydes. The product is then analyzedparticularly for mercaptan retention.

The determination of the amount of methyl mercaptan in each compositionis made by heating treated samples to 56 C. for two hours and thencollecting the vapors above the samples. These vapors arechromatographed at 30 C. on a six-foot column containing 10% of amixture of cyanoethylmethyland cyanodimethyl 3 in Table I below.Untreated malathion is employed as the control.

Added by partitioning from saturated aqueous sodium sulfate solution.[Theoretical: 2%.]

Example 2 The effectiveness of ethyl glyoxylate for deodorizingmalathion (O,'O-dimethyl phosphorodithioate of diethylmercaptosuccinate) is demonstrated by utilizing from to 1.5% by weightof ethyl glyoxylate.

Several samples of technical grade malathion having a" rather strongoffensive mercaptan odor are mixed with the treating aldehyde. Suchsamples are placed on a water bath maintained at 56 C. for a period of34 days and periodically analyzed for methyl mercaptan, a particularlymalodorous component.

Determination of the amount of methyl mercaptan present in untreatedmalathion is accomplished by means of gas-liquid chromatography. Themalathion samples are heated at 56 C. for two hours. Vapors above thesamples are collected and chromatographed at 30 C. on a six-foot columncontaining 10% of a mixture of cyanoethylmethyland .cyanodimethylsilicone gum. Each determination is accomplished with a flame ionizationdetector. The amount of methyl mercaptan present in each sample isreported in Table 11 below.

TABLE II 20 time, is N('N-1).

temperature held at either 34 C. or 60 C. for either 15 or 41 days.Untreated samples of each material stored under identical conditions areemployed as controls. After storage for 15 or 41 days, the samples are 5evaluated by the known Scheffes method of paired comparisons. Thecomparisons are randomized amongst a panel of judges with eachobservation or comparison of a sample pair being made by a differentjudge. To eliminate a possible bias due to the desensitization of the01- factory nerves by the first sample prolfered, thereby causing apreference for the second, both orders of presentation for each samplepair are obtained for evaluation. In addition, all panels have been runin duplicate, and the degree of reproducibility has been good.

From a statistical point of view, to determine the relative preferenceof N samples, each sample is compared with each of the other (N-l)samples. With both orders of presentation -for each pair of samples, thenumber of permutations or combinations for N samples, two at aPreferences are scored on an arbitrary numerical scale, 12 for a higherpreference, and 0 for no preference. The sign of the score depends uponwhether the preference is for the first or second sample proffered. Thepreferred sample receives a positive score when it is proffered firstand negative score when proifered second. In the absence of adesensitization effect and random or systematic error, the sum of thescores for both orders of presentation for each sample pair would bezero. When there is no preference for either sample, a 0 score isentered for the sampled proffered first.

A scoring box is made up with the row scores pertaining to thepreference of samples proffered first and column scores pertaining tothe preference of samples proffered second. The total score for eachsample is obtained by making a sign change when adding the column scoresto the row scores. After the rows and columns have been added, andallowing for the necessary sign changes, the sample with highestpositive score will be the most preferred and the other samples can beranked in descending order. The results of the above tests are presentedin Table III below.

Untreated, Technical 0,0-Dimethyl Phosphorodithioate ofDiethylMercaptosuccinate MethylMercaptan (p.p.m.) Days in 56 C. BathTechnical plus 0% ethyl glyoxylate 81 1,300 622 6, 300 Technical plus0.5% ethyl glyoxylate. 0 0 0 2, 560 Technical plus 1.0% ethylglyoxylate. 0 0 0 44 Technical plus 1.5% ethyl glyoxylate 0 0 1.9 0

Example 3 Deodorization of 0,0- diethyl S- (ethylthio)methylphosphorodithioate is demonstrated by the following procedure wherein2.0% by weight of ethyl glyoxylate is mixed with samples of thetechnical grade material and with distilled technical grade material andstored at a 75 various aldehydesi The data also show that the additionof 1.5%

TABLE III [Odorpreierence scores of 0,0-diethyl S-(ethylthiomethyDphoshorodithioatc [Thimet] containing 2.0% ethyl glyoxylated by wei ght] OOripr PanebScore,

ven a s Thimet Sample Temp, y m ven Technical 84 6 3 Technical plusEthyl Glyoxylate 34 4 1 0 D stilled 34 0 7 Distilled plus EthylGlyoxylate 34 10 11 Example 4 In this example, the marked odor controlcapacity of n the treatment of phosphorodithioates is demonstrated bythe following tests wherein 0,0-dimethyl phosphorodithioate of diethylmercaptosuccinate, O,()-diethyl S-(ethylthiomethyl) phosphor-odithioateand 0,0-diethyl S-(N-methylcarbarnoylmethyl)phosphorodithioate aretreated with from about 1% to about 4% by weight of a variety ofaldehydes and mixtures of such al dehydes. In these tests, the technicalgrade phosphorodithioatesare admixed with aldehyde, permitted to standfor about 24 hours, and then sniffed to determine the level of odorcontrol achieved by the various treatments. Untreated technical gradematerial is used as a control. The results of the tests appear in TableIV below.

3. A process according to claim 1 wherein the aldehyde present rangesbetween about 1% and about 4%, by weight.

4. A method according to claim 1 wherein the aldehyde is ethylglyoxylate.

. 5. A method according to claim 1 wherein the aldehyde ismethylprotocatechuic aldehyde.

6. A method according to claim 1 wherein the aldehyde isethy-lprotocatechuic aldehyde.

7. A process according to claim 1 in which the malodorous thiophosphateis 0,0-dimethyl phosphorodithioate of diethyl mercaptosuccinate.

TABLE IV Sample Additive Percent Odor Control Added 0,0-dimethylphosphorodithioate of diethyl mer- Benzaldehyde 1 Good, ahnond-likeodor.

captosueeinate.

D Ethyl glyoxylate 2 Good, little or no odor.

Methylprotocatechuic aldehyde. 1 Good, slight vanilla odor.Ethylprotocatechuie aldehyde 1 Good, slight vanilla odor.

Control no additive Benzal ehyde Methylprotoeateehuie aldehydeEthylprotocateehuie aldehyde Poor, malodorous. Good, strong almond odor.

4 Good, vanilla odor.

4 Good, vanilla odor.

2 Good, Slight vanilla odor. 2

Benzaldehyde Good, slight almond odor. Methylprotoeatech e aldehyd Good,slight almond odor. Salieylaldehyde Good, nitrobenzene-like odor. DControl, no additive Poor, malodorous. Op-diethylS-(N-methylcarbamoylmethyDphos- Ethylprotocatechuic aldehyde 1 Good,vanilla odor.

phorodithioate.

Do Control, 110 additive Poor, malodorous.

I laim; 8. A process according to claim 1 in Which the mal- 1. A methodfor the upgrading of an untreated, malodorous thiophosphate is0,0-diethyl S-(ethylthiomethyl) odorous, mercaptan-containingthiophosphate pesticidev phosphorodithioate.

9. A process according to claim 1 in which the malodorous thiophosphateis 0,0-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate.

10. A method according to claim 1 in which the treating temperature ismaintained between about 0 C. and about C.

No references cited.

CHARLES E. PARKER, Primary Examiner.

BERNARD BILLIAN, FRANK M. SIKORA,

Assistant Examiners.

1. A METHOD FOR THE UPGRADING OF AN UNTREATED, MALODOROUS,MERCAPTAN-CONTAINING THIOPHOSPHATE PESTICIDE WHICH COMPRISES THE STEPSOF: TREATING SAID MALODOROUS, MERCAPTAN-CONTAINING THIOPHOSPHATE WITHBETWEEN ABOUT 0.5% AND ABOUT 5%, BY WEIGHT, OF AN ALDEHYDE, WHEREBY AHIGH BOILING MERCAPTAN-ALDEHYDE COMPOUND IS FORMED, AND, THEREAFTER,RECOVERING AN ODOR-IMPROVE, STORAGESTABLE THIOPHOSPHATE.